One month ago, after reading some of Ellen Boughn's articles about keywording and some other useful blogs giving tips about keywording I finally decided to make a full re-keywording of my images. I was postponing it for quite a long time but finally decided to make it.
With almost 400 images in my portfolio it took me about 4 days to revise every single one of them. Before getting to work I made a list of all the important hints and tips I had to pay attention at. On the top of the list I put hamburger ≠ eating, referring to one of Ellen Boughn's tips : if the image is showing a hamburger on white background keywords like eat, eating would be irrelevant. And it makes perfect sense! If someone would've wanted an image of the very action of eating he'd probably used the keyword eat or eating.
In the process of revising my images I found a lot of them having that issue with description and keywords. I had used a lot of words describing what MIGHT happen to the subject from the image, not the subject itself. So I replaced all irrelevant keywords with more descriptive ones, got rid of all "the"s and "a"s in the titles (as they don't reflect on search result) and removed all unnecessary capital letters.
And not long after, my efforts started to pay off. I started selling images which had barely any views before that, not to speak of sales. Of course, there is no way I can be 100 % sure these sales came as a direct result of the changes I made, but one thing I notice now is that more and more of my recent sales were made after searching with keywords I added during the re-keywording process.
So do not underestimate the power of re-keywording. There is always a hidden potential in it.